*
     * @param map the source map.
     * @param key the key to look up.
     * @return the map value, or {@code null} if not found or not a map.
     */
    @SuppressWarnings("unchecked")
    protected Map<String, Object> getMapValue(final Map<String, Object> map, final String key) {
        final Object value = map.get(key);
        if (value instanceof Map) {
            return (Map<String, Object>) value;

 *
 * <p>Entries in the map can be in the following states:
 *
 * <p>Valid:
 *
 * <ul>
 *   <li>Live: valid key/value are set
 *   <li>Loading: loading is pending
 * </ul>
 *
 * <p>Invalid:
 *
 * <ul>
 *   <li>Expired: time expired (key/value may still be set)
 *   <li>Collected: key/value was partially collected, but not yet cleaned up
 *   <li>Unset: marked as unset, awaiting cleanup or reuse
 * </ul>
 */

    }

    @Override
    public boolean containsKey(Object key) {
      assertTrue(Thread.holdsLock(mutex));
      return super.containsKey(key);
    }

    @Override
    public boolean containsValue(Object value) {
      assertTrue(Thread.holdsLock(mutex));
      return super.containsValue(value);
    }

    @Override
    public @Nullable V get(Object key) {
      assertTrue(Thread.holdsLock(mutex));

      if (currentValue != null) {
        alertListenerIfPresent(key, currentValue, RemovalCause.REPLACED);
        return put(key, value);
      }
      return null;
    }
  }

  @Override
  public boolean containsKey(@Nullable Object key) {
    synchronized (lock) {
      return cachingHashMap.containsKey(key) && !isExpired(cachingHashMap.get(key));
    }
  }

  @Override

    K key = checkNotNull(entry.getKey());
    V value = checkNotNull(entry.getValue());
    if (map.containsKey(key)) {
      // When a collision happens, the colliding entry is the first entry
      // of the tail map.
      Entry<K, V> previousEntry = map.tailMap(key).entrySet().iterator().next();
      throw new IllegalArgumentException(
          "Duplicate keys in mappings "

                        PopulatableMapAsMultimap.create();
                    populateMultimapForKeys(multimap, elements);
                    return multimap.build().keys();
                  }
                })
            .named("Multimaps.forMap.keys")
            .withFeatures(FOR_MAP_FEATURES_ANY)
            .suppressing(getCountDuplicateInitializingMethods())
            .suppressing(getSetCountDuplicateInitializingMethods())

     * Removes the entry corresponding to the specified key from the map entries.
     *
     * @param key
     *            the key
     * @return the removed entry, or {@literal null} if there was no entry for the key
     */
    protected Entry<K, V> removeMap(final Object key) {
        int hashCode = 0;
        int index = 0;

        if (key != null) {
            hashCode = key.hashCode();

@GwtCompatible
final class CollectPreconditions {

  static void checkEntryNotNull(@Nullable Object key, @Nullable Object value) {
    if (key == null) {
      throw new NullPointerException("null key in entry: null=" + value);
    } else if (value == null) {
      throw new NullPointerException("null value in entry: " + key + "=null");
    }
  }

  @CanIgnoreReturnValue
  static int checkNonnegative(int value, String name) {

  /**
   * Returns the tag attached with [type] as a key, or null if no tag is attached with that key.
   *
   * The tags on a call are seeded from the [request tags][Request.tag]. This set will grow if new
   * tags are computed.
   */
  fun <T : Any> tag(type: KClass<T>): T?

  /**
   * Returns the tag attached with [type] as a key, or null if no tag is attached with that key.
   *

            // meta
            extractData.getKeySet().stream().filter(k -> extractData.getValues(k) != null).forEach(key -> {
                final String[] values = extractData.getValues(key);
                metaDataMap.put(key, values);

                // meta -> content
                if (fessConfig.isCrawlerMetadataContentIncluded(key)) {
                    final String joinedValue = StringUtils.join(values, ' ');